The present application is based on and claims priority from Japanese Patent Application 2000-354516, filed Nov. 21, 2000, the contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a rectifier unit of a vehicle AC generator for a passenger car, truck or the like.
2. Description of the Related Art
It is known well that a vehicle AC generator is provided with a rectifier unit that includes a pair of three-phase full-wave rectifier circuits. For example, such a rectifier unit is comprised of a positive side heat sink and a negative side heat sink. Each heat sink has six diodes that are force-fitted or soldered thereto. The positive side and negative side heat sinks are fixed by a bolt to a frame of the AC generator with an insulation member being interposed between the heat sinks of the pair. However, because this type of the rectifier unit has twelve diodes, the number of parts and manufacturing steps are comparatively large. It is also difficult to make the size of the AC generator compact.
JP-A8-205498 and JP-A-7-231656 propose a metal case accommodating two semiconductor chips that are different in polarity from each other in order to reduce the number of parts and the size of the AC generator. However, two semiconductor chips that are different in polarity from each other in a metal case necessitates additional expensive structure to insulate the chips and to distinguish the polarity of the semiconductor chips.
Therefore, a main object of the invention is to provide an improved rectifier unit of a vehicle AC generator that is compact and inexpensive.
According to a feature of the invention, a rectifier unit of a vehicle AC generator including a plurality of metal cases, a pair of first and second semiconductor chips that has the same polarity with each other disposed in each said metal case, a pair of first and second lead wires connected to the pair of first and second semiconductor chips and a pair of first rectifier circuit connected to the first lead wire and second rectifier circuit connected to the second lead wire.
Therefore, the number of metal cases is reduced without providing a complicated insulation arrangement so that manufacturing steps and cost can be reduced.
According to another feature of the invention, the rectifier unit may further include a plurality of insulation members. The insulation member is disposed between the first semiconductor chip and the second semiconductor chip disposed in each metal case.
According to another feature of the invention, a clad metal member of copper layer, iron-nickel layer and copper layer is disposed between the pair of semiconductor chips and the bottom of the metal case.
Therefore, the clad metal member moderates stress caused by a difference in thermal expansion between a solder layer and a pair of the semiconductor chips.
According to another feature of the invention, the rectifier unit may further include a pair of heat sinks having a plurality of mounting holes. Each metal case has a knurled outer surface to be force-fitted to one of the mounting holes of the heat sinks.